Loon families need a sizeable territory to successfully raise their chicks. A loon family with a pair of chicks will eat something like a half ton of (mostly) fish during the season. Loons will fight to defend their territory. One result of the growing loon population is more frequent disputes over territory. Most of these are settled with some vocalization and displays. Some get more serious and some are serious enough to kill one of the combatants. Here are a few shots from an all-out fight on Symes Pond in Ryegate, Vermont in May 2019. The home team was an established pair with a egg in their nest.
After some posturing, one loon went after another - hard to tell who is whom since they all dress alike. This is the loon being chased, rowing across the water with his wings (or 'oaring' if you're from across the pond).
Another shot of wing rowing.
Eventually, the chasing loon caught up with the chased and they fought, trying to drown each other.
While watching, I thought that one had succeed in drowning the other. They'd been fighting not far from shore, both went down and only one came up. The second eventually appeared from under some of the brush along the shore. Fighting resumed and one was chased about 25 feet up the shore. It rested there for many minutes before slowly making its way back to the water. Once afloat, it took off and left the pond. I believe the original pair had successfully defended the pond. The pair that remained on the pond laid a second egg and eventually hatched two chicks.